1. Field of the Invention
The present invention relates to an optical device which controls light utilizing the change of position of fluids.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT International Application) No. 2007-531917 discloses a display device based on an electro wetting effect. This display device includes a structure where two fluids, which are mutually immiscible, are disposed between two substrates which respectively include an electrode. A fluid possessing conductivity or polarity is used as one of the fluids. With this display device, the wettability of the fluid possessing conductivity or polarity can be controlled by applying a voltage between the electrodes of the respective substrates. Accordingly, for instance, if one of the two fluids is colored and the other fluid is transparent, the intensity of the light that is transmitted through the respective fluids or the intensity of the light that is reflected by the respective fluids can be controlled according to the state of the respective fluids after movement. As the foregoing two fluids, illustrated are, for instance, oil containing a dye as one fluid, and water as the other fluid. A display device based on this kind of electro wetting effect is advantageous in that it is compatible with both a reflective display and a transmissive display, capable of realizing the same level of reflectance (approximately 50%) and contrast ratio as a paper medium in the case of using a reflective display, and has a relatively fast switching speed (for instance, 10 milliseconds or less).
Meanwhile, in the foregoing related art, after electrically controlling the position of the fluids, it is necessary to continuously apply a drive current in order to maintain the foregoing state. In other words, there was no memory effect in relation to the state after the fluids are moved. Thus, for example, there is a drawback in that it is difficult to use the foregoing related art for usages which are demanded of ultra low power consumption such as with a so-called electronic paper or the like. Moreover, since there is no memory effect, it is necessary to provide a switching element such as a thin film transistor to the respective pixels when applying the technology of the foregoing related art to a dot matrix-type display device, and there is an additional drawback in that the simplification of the structure is difficult.